Every week for over a year, the future owners of this home in the Laurelhurst neighborhood—we’ll call the press-shy couple Mr. and Mrs. Laurelhurst—met with architects to dream up what to build on the southwest-facing Lake Washington property they purchased in 2012.

“I was on Pinterest a lot,” says Mrs. Laurelhurst, who would email images of billowy drapes, curved archways, and rooms with thick stucco walls common in Old World homes but rarely seen in Seattle. They didn’t want Pacific Northwest, after all. They wanted Tuscany.

For Tim Hossner and Robin Cinamon of Rho Architects, it became clear their job in these meetings was to marry a desire for romantic design with Mr. Laurelhurst’s interest in modern technology. “We really played up the classic forms,” he says, underneath which an energy-efficient home hides, complete with a state-of-the-art lighting system and appliances, solar panels, and geothermal heating.

As for the classic forms, Hossner and company went with eight-inch thick walls, rather than the traditional six inches, which keep the home well insulated and provide that classic Mediterranean feel. They covered the exterior with six layers of stucco, left unsealed to allow a patina of plantlife and age to appear over time.

Inside, clean lines and subtle detailing became the focus: unusually high windows in the kitchen and living room, exposed black steel beams, and wide-plank walnut flooring. The uniformly warm gray walls create a quieter background for the couple’s art collection, complete with gallery-style lighting. And, just to sneak in a touch of traditionally Northwest architecture, the exterior textures extend along a dividing wall between the living room and entryway; a bridge between the inside and out.

Interior designer Lisa Staton dove into photos of Italian villas when sketching out the visual vocabulary of the interiors. “We really wanted to treat it like a Mediterranean house, with materials repeating,” she says, since in Italy there may only be one quarry from which to draw materials. The kitchen counters are made from quartzite—more durable than marble—and limestone echoes throughout the house, including the fireplace.

For furnishing, Staton focused on textures and layers as opposed to color or pattern, like natural linen drapes with a wrinkled handmade look juxtaposed against stark black window frames. But that still left room for luxury, as in the rock crystal chandelier above a rustic farm table.

Now, walking in the front entryway, which looks across the length of the house and down the stairs through windows that frame Lake Washington, it’s easy to imagine warmer waters. And that’s exactly the point. Mr. Laurelhurst remembers when they had recently returned from a month-long trip in Europe. “You leave Sea-Tac, you’re driving on I-5. But when we pulled up to this house it was like, ‘Ahhh, we’re back!’ ”